


you came well equipped with a gun on your hip and some poison on your lips

by eugenides (newamsterdam)



Category: Star Trek, Star Trek: Alternate Original Series (Movies), Star Trek: Mirror Universe
Genre: F/M, M/M, Mirror Universe, Threesome - F/M/M
Language: English
Status: Completed
Published: 2013-11-23
Updated: 2013-11-23
Packaged: 2018-01-02 11:15:09
Rating: Mature
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 3,349
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/1056109
Author URL: https://archiveofourown.org/users/newamsterdam/pseuds/eugenides
Summary: <blockquote class="userstuff">
              <p>Five times Carol Marcus tilted Leonard McCoy's word off its axis. And one time everything shifted back into place.</p>
            </blockquote>





	you came well equipped with a gun on your hip and some poison on your lips

Carol Marcus waltzes into his life like she owns it.

The first time, she’s just a whisper. He’s standing outside of Kirk’s quarters at HQ, wondering what the hell he’s doing. The only time he gets even a moment of peace is when they’re docked, when he’s got his own quarters in Medical and isn’t under Kirk’s constant watch. The _Enterprise_ is, after all, the captain’s own private panopticon, and more often than not his gaze falls on McCoy. 

And yet, for reasons he can’t fully explain to himself, here he is. And while he’s been standing outside Kirk’s door, deliberating with himself, the door has slid open with a hiss.

“McCoy,” Kirk says even, face impassive. There’s a cut across his cheek, a chunk of skin missing from his forehead. His eyes are cold, more so than usual. “What the fuck are you doing here?”

It’s not even so much of a question. He might as well have said _I didn’t summon you_. But McCoy just purses his lips, holds up his medkit. 

“You were in a goddamn firefight. As ship’s doctor…” He trails off as Kirk throws back his head and begins to laugh. 

“Doctors,” Kirk says with a roll of his eyes. But he moves aside in the doorway, lets McCoy in. The doctor doesn’t bother to ask questions about the fight, about John Harrison’s failed coup that ended with a dozen senior officers dead. Instead, he follows Kirk to the chaise lounge in his antechamber, kneels on the floor beside it as Kirk sits. 

This time, Kirk even waits until McCoy’s cleaned all his wounds, run a basic regen over them, before strong hands clench around McCoy’s shoulders and push him bodily away. 

“Don’t be an idiot,” McCoy can’t help but bite out. He’s still holding up the dermal regenerator, knows that if he can’t go a few more rounds Kirk’s pretty face will scar. 

Kirk just raises one brow, pointedly, an expression he’s picked up from either Spock or McCoy himself or both. Either way, he’s perfected it, daring McCoy to continue and looking perfectly dangerous as he does. 

McCoy pauses, words caught in his throat, and in the next moment Kirk’s slunk off the couch to crouch beside him. His hands go up, one knocking the regenerator out of McCoy’s hands and the other coming up to cup the doctor’s jaw. 

“I had plans for the lot of them, all the ones who died today,” Kirk says idly. It’s never a good mood, that pitches his voice that way. McCoy swallows convulsively. “And fucking Marcus didn’t even have the good sense to die.”

Everyone knows Alexander Marcus, especially after he took out Barnett six months ago. He’s the head of the Imperial Fleet, one of the most powerful men in the galaxy. And Harrison’s attack happened on his watch. 

“Hmm.” Kirk is musing, considering, as he pushes McCoy onto his back and drapes the full weight of his body over him. “I wonder how Carol would feel if I killed her daddy.”

“Carol?” McCoy asks. The best strategy is always to keep his mouth shut, but even after years with the Fleet—with Kirk—he hasn’t learned that lesson.

“No one you need to concern yourself with,” Kirk assures him, claiming his lips in a biting kiss.

If only that had been true.

*

They’re already back on the ship by the time McCoy actually meets her. He’s in sickbay, the part of the _Enterprise_ that is under his control—the part of his life that’s under his control—at least until Kirk says otherwise. They’d left San Francisco so quickly that McCoy hadn’t even been able to do inventory, let alone call in more nurses to replace the six that’d been lost on their last mission. None of that would excuse a less-than-efficient sickbay, however. 

It takes him a minute to notice her. She stands in the doorway and watches him counting vials, arms crossed loosely over her chest. When he finally does look up, she smiles.

She’s blue-eyed and blonde, but seems worlds away from Kirk’s supernova eyes and burnished hair. No, her eyes are like water, not stars or sky. Their colors seems to shift as she turns her head, first pale and icy and then a deep blue-green. Her hair’s cut short around her ears, not a strand out of place. 

“Doctor McCoy,” she says, her voice warm and accented as he doesn’t expect.

“Yeah?” 

“I’m Carol Marcus.” She inclines her head. She’s a lieutenant, technically ranked below him, but with her connections she’s got more power than he could ever dream of. But it’s never been in him to be easily intimidated.

“I know.” His voice is gruff. He keeps counting vials, occasionally dipping one back and forth to watch the colored liquids shift. “Doctor in applied physics, specialist in advanced weaponry. The bomb Harrison used was your design.”

Her pretty features are marred for an instant—just an instant—as they pull into a scowl. “Yes,” she says after a moment’s pause. “And you should know, I don’t react kindly to people who use my inventions without my permission.”

McCoy shrugs. The politics of this are beyond his caring. He knows that Pike died before Kirk wanted him to, and Marcus is still alive. Those facts, and how they affect Kirk’s moods, are what ultimately matter to him. That, and keeping Kirk’s crew of psychopaths alive as they chase on John Harrison across the known universe. 

He doesn’t realize how close Carol’s gotten until she’s standing directly in front of him. When she speaks next, her voice is soft and low. “I know he keeps you tucked away here, out of sight.”

“I’m a doctor. Where the hell else would I be?”

She continues on as if she hasn’t heard. “Everyone else on this ship wears their talents on their sleeves. Their genius, their predilections. But you…”

“What about me?” McCoy turns away abruptly, tucks his tray of vials onto a shelf and selects a new one. He feels Carol’s hand when it lands on his shoulder. 

“You’re a mystery.” 

He shifts away from her. He doesn’t know what kind of game she’s playing, because as far as he’s concerned he’s the most straightforward person on this damned boat. He doesn’t coat his intentions in razor-sharp smiles, doesn’t play complex political games. He’s the flagship’s CMO because he’s the best doctor in the Fleet—not that there’s much competition, when most of the others behave as butchers. 

“I’d like your help, Doctor McCoy,” Carol Marcus tells him, once she’s circled around to look him in the eye once more. “You’re a genius at biology, even if you don’t advertise the fact. I could use a consult.”

He should be worried, about the way she’s smiling at him. But the only emotion that bubbles up in his chest is pride.

*

Kirk’s never begrudged him access to the labs, even though they are Spock’s domain. Carol Marcus is an intrusion, to the First Officer, and he makes it clear the first time McCoy accompanies the other doctor there. 

“What are you doing here, Lieutenant?” The Vulcan asks, face like marble and voice like oil—slick and opaque. 

“I’m a scientist, Mr. Spock,” Carol says primly. “I didn’t realize I needed your permission to do my job.”

“I am not convinced, Lieutenant, that your job aboard this ship is not entirely redundant. We have both weapons specialists and scientists. Your collective expertise is nothing unique.” 

Having known the First Officer for years, McCoy knows his tells. He can see the way the Vulcan’s lip is twitching, just slightly. Lieutenant Marcus has made him genuinely angry. And if that isn’t a reason to like her, what is?

“You can take it up with Captain Kirk, then,” Carol’s saying. “Until then, do try and stay out of the way.” She bares all her teeth in a smile, sapphire earrings glinting as she tosses her head. Uhura’s always preferred gold, from the glint of her daggers to the thick bangles she wears around her forearms. Carol, on the other hand, is all silver and cold. Maybe the distinction is how Spock decided he didn’t like her.

She brushes past Spock, motions for McCoy to follow her. Before he can, Spock holds him back.

“I would be very careful about what you are doing, Doctor.”

“Thought we already established that you couldn’t do much by threatening me, Spock.”

“It is not a threat. Technically, it is a warning.”

McCoy fixes Spock with the full force of his glare. They’ve never gotten along, but they’ve always agreed on one thing—both of their interests are best served by keeping James Kirk alive and as head of the _Enterprise_. McCoy’s part in that is literal, putting the captain back together again every time he falls prey to his own reckless ambition. Spock’s methodology is more subtle, political machinations revolving around impeccable and impartial logic. 

McCoy realizes, for the first time, that he doesn’t know where Carol falls in this paradigm. 

“Be careful, Doctor,” Spock says, before turning away. McCoy takes it for what it is—both threat and warning—before joining Carol in one of the smaller, more private labs.

She smiles at him warmly, eyes deep like the lakes he used to swim in as a boy in Georgia. She’s already got plans pulled up on the view screen, gestures towards them grandly with a glint in her eyes. 

“Doctor McCoy,” she says, “I’d like to introduce you to Genesis.” 

As she walks him through it, proud as a mother of her child, McCoy finds himself wrapped up in her words. Her own genius.

*

Kirk, Uhura, and Spock go down to Qo’noS because Kirk, in his infinite wisdom, wants to deal with Harrison himself. Carol invites McCoy down to the labs, and while he helps run simulations on virtual ecosystems she makes small explosions in contained environments. It’s all rather peaceful, and it keeps McCoy from pacing on the bridge while Sulu— _Sulu_ —is left in charge. 

He doesn’t know how many hours it’s been when he finally sits back from the console, rubs a hand over tired eyes. 

“Leonard,” Carol says, waltzing over to him. She started using his first name after they’d begun working together. She’d rationalized, to him, that he’d never think of her as Marcus while her father lived, so why should she think of his as McCoy? Like so much else she says to him, it had made sense at the time.

“Leonard,” she says again, and holds out a tumbler filled with electric blue liquid—Romulan ale. “We’re so close. We should celebrate.”

He takes the glass and raises it towards her in a toast. He may not understand her, but the woman is making a deadly weapon out of the principles of life, and he can’t help but be awed. 

He knocks back four glasses before she settles herself in his lap. Somewhere, distantly, he realizes that this might be the stupidest thing he’s ever done. But it’s easy to drown that voice out, to lean down and kiss her. She opens her mouth readily, lets him slip his tongue between her lips and control the pace for a moment. But only a moment.

Suddenly she’s the one in control, tongue scraping over his teeth and arms wound around his neck. He brings his hands up to the small of her back, and she shifts, one leg on either side of him. For such an impressive person—for such an impressive mind—she seems to weigh almost nothing as he picks her up. Her legs are clamped around him, now, and as he sets her down on one of the lab’s immaculate countertops, she places her booted feet on his shoulders and forces him down to his knees. 

“Leonard,” she breathes, and the smile she flashes him through kiss-reddened lips is bright and feral.

For the briefest moment, he thinks he can see Kirk standing over her shoulder, looking down at him with condemning eyes. The next second, he shakes off the sensation and pulls Carol’s legs apart. 

He’s kissing her thighs, working his way up as she runs her hands through his hair and sighs happily. He pushes her skirt out of the way, pulls down her underwear and laps his way into her with so much intensity that she throws back her head and moans. 

Later, when she’s laying back on the countertop and he’s bracing his hands on either side of her and they’re both breathing heavily, she looks down at him with affection. “Leonard,” she says, in the same tone she uses to dictate chemical equations—utterly assured of her own opinion, her own rightness, “I knew you were special.”

McCoy tries to hide his smug smile, but then decides not to bother. It’s been so long since he’s done anything of his own volition, since he’s enjoyed a woman at all. Too often he’s the one being taken apart, and the fact that he’s reduced Carol Marcus—not an admiral’s daughter, but a brilliantly mad genius and an impossibly beautiful woman—to gasping his name sends fire sparking through his already sensitive nerves. 

“He’s gonna kill us, you know,” he says, barking out a laugh.

She leans down, cups his face in her hands, eye glinting possessively. “Oh, he might try.”

*

As it turns out, he doesn’t get the chance. James Kirk, determined against reason to kill John Harrison, will not accept loss. And he pays for victory with his life. It’s Spock, eyes lit with dark fire, who rips the man limb from limb, as Uhura stands to one side and watches with her arms crossed over her chest. The secret of Harrison’s immortality, his superior strength and intellect, are lost as his blood dries on the ground of San Francisco. 

McCoy can’t bring himself to care, much, because he’s standing over Kirk’s body and holding a PADD. There are people standing around him, waiting for him to declare the time of death and sign the death certificate. To officially declare that the brightest star in the universe has gone out.

But fuck that, really. 

Carol’s standing beside him, her eyes pale and cold. “It wasn’t supposed to be him,” she says quietly.

McCoy stares at her.

“Harrison wasn’t supposed to get him,” she says again.

His jaw works furiously, something pounding in his ears until the words burst out of him. “What did you do?” he demands. 

She looks at him and smiles softly. There’s affection, there, but also something darker and deeper. He realizes, so belatedly, that he never has understood her. 

“I wanted my father dead,” she says. “And I always get what I want.”

Harrison had Carol Marcus’ bomb, and used it to take out a supposedly-secret meeting of the highest brass. Alexander Marcus had escaped that encounter, but not the next. And now James Kirk is lying dead in front of him. 

“What the fuck did you do?” He’s screaming, now, knows when this comes to light it’ll be official, the feeling that’s building in his chest—that this is his fault, too. 

Carol doesn’t look repentant. She stares him down, lifts her chin. “I care for you, Leonard. Maybe more than anyone else left in this world.”

“Shut up,” he barks.

“No,” she contradicts him easily. “Listen to me. He hid you away. He controlled you. Why are you so upset, now?”

“You don’t know anything,” he tells her. All he can think about is the past few weeks, while Kirk pursued Harrison and McCoy let himself be distracted. By Carol Marcus and her intoxicating genius. By her weapons and her projects. By Genesis.

The breath stops in his throat, choking him. Genesis.

“Get me your formula,” he says to her, fire in his voice.

“Leonard, what—”

“Now!”

It isn’t a sure shot, and he knows it. Her idea is death from life. Reversing the process might be impossible. But he has to try.

His hands are sure and steady as they lower Kirk into a cryotube, and for hours afterward as he and Carol pour over consoles and rearrange chemical formulas. 

When Spock and Uhura step into sickbay seven hours later, splattered with Harrison’s blood, McCoy lifts his head and gives them both a grim smile. 

“You’re gonna be glad, Spock,” he says roughly, “that you didn’t toss Doctor Marcus off this ship, like you wanted.”

&1

San Francisco is quiet, reeling from the destruction of months earlier. Usually, the benefit of being the capital is that the violence is outsourced, sent to space with the Fleet so that the most powerful don’t have to face it directly.

McCoy supposes that was the theory Alexander Marcus subscribed to, before his death. 

Now, he’s standing in the antechamber of Kirk’s rooms, wondering if his own life is about to end. He’d brought Kirk back from the brink, the end, and now he might be paying for the foolhardy, emotional decision. 

Somehow he can’t find it in himself to regret it.

He stands stock still, dressed fully in dress uniform, waiting for Kirk to arrive. The minutes trickle by, the apprehension rising in his chest. Then, from behind him, he hears the breath of the doors sliding open.

“Oh, Jimmy, you were right. That uniform.”

He’s turning at the sound of her voice before he can stop himself, but finds himself struck dumb by the sight in front of him. James Kirk, alive and well, but that isn’t the surprise. It’s his complacent smile, only slightly sharp. It’s the way Carol Marcus is at his arm, beaming at McCoy. It’s the way she leans up to kiss Kirk’s cheek before taking a few steps towards McCoy and kissing him on the lips.

He can’t help but respond, even knowing Kirk is right there. He dips Carol as he kisses her, her hands fisting into his hair.

Somewhere above him, Kirk laughs.

“It’s a pretty picture,” he says. McCoy steps away from Carol and straightens up. Kirk is looking right at him, gaze sharp. Then he closes the space between them, puts one hand on the back of McCoy’s neck and the other like a vice on his hip.

“You missed me so much, you went and found a replacement?” he asks, and McCoy would be stupid not to hear the threat in his voice. Maybe he is stupid, because he never realized it before. His blonde-haired, blue-eyed geniuses. Both from the oldest of imperial families, who must’ve grown up at court. Together. 

“But Carol… and Harrision…” He’s stuttering, and he doesn’t care. “You know what she did.”

Kirk nods, self-assured as ever. “I could’ve done without dying. But now, thanks to you two, we have both life and death in our hands.”

McCoy doesn’t understand. He shakes his head.

“Jimmy,” Carol says, chidingly, “don’t tease him.”

For a second he can’t breathe. Then McCoy’s throwing back his head and laughing, almost hysterically. He barely registers the fact that Kirk’s stripping him out of his jacket, his pants. He doesn’t feet it when Carol comes up behind him, wraps her arms around his waist and plasters herself against his bare back. 

Somehow, they’ve ended up in Kirk’s bedroom. Somehow, he’s lying on Kirk’s bed. Somehow, he’s surrounded by the both of them.

“He looks so confused,” Carol says, and her voice is both indulgent and mocking.

“He’ll catch on, eventually,” Kirk assures her, and that’s when McCoy feels his fingers inside of him, yelps and arches upwards at the sensation. “See?”

Carol turns McCoy’s head for him, lavishes his mouth with her tongue. “We all play dangerous games, Leonard,” she tells him, her breath soft against his face.

Kirk’s turning him over, now, coming up behind him to align their bodies. His voice is hot, whispered into McCoy’s ear. “And no one would count this as a loss.” He sounds almost impressed. 

“Yeah?” McCoy manages to ask. “And what’d I win?”

Between the two of them, they show him.

**Author's Note:**

> My interpretation of an Into Darkness scenario in Mirrorverse. There's probably a longer, Carol-POV version of this lurking around somewhere on my computer but I'm not sure if it's worth telling. I see the events of the movie as taking place over the course of a few weeks, as opposed to a few days. Carol's projects and expertise are based on her TOS counterpart. Title comes from Margot & the Nuclear So and So's "Tall as Cliffs."


End file.
